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BIOACCUMULATION Chapter 2.3 Chemical Pollutants • Humans have been introducing synthetic (man-made) chemicals into the environment. Some examples are: PCBs (polychlorinated biphenyls) widely used in paints, plastics, lubricants up to 1977 DDT (an insecticide for mosquitos) now banned in many countries Dichloro-diphenyl trichloroethane DDT DDT was first used in WWII to protect against diseases such as typhus and malaria. It is cheap and effective as an insecticide – so it began to be manufactured for home use. Before it was banned in 1972 by the EPA for use in agriculture, 1,350,000,000 pounds of DDT had been made in North America. EFFECTS OF DDT • DDT is found to have estrogenic effects: – Causes reproductive disorders – Weakens the shells of eggs (eggs break or do not hatch) – Can also cause nervous system/ immune system disorders in animals DDT – Used as an Insecticide • DDT is used today in such African nations as Zimbabwe and Ethiopia to control mosquitoes and the tsetse fly. • These two insects cause serious diseases, such as malaria and sleeping sickness. PCBs • Used widely in products like paints, plastics, etc as softening agents from the 1930’s – 1970’s • Banned in North America in 1977 • There are 209 different congeners (different chemical structures) • PCBs interfere with immune function making an organism more susceptible to disease (ex: cancer) Heavy Metals • Heavy metals are metallic elements that are toxic to organisms. – Levels of lead in the soil have increased due to human activities. • Lead is not considered safe at any level. • Many electronics contain lead and must be recycled carefully. • Lead can cause anemia and nervous and reproductive system damage. Heavy Metals (con’t) – Cadmium is also found in low levels naturally. • Cadmium is used in the manufacture of plastics and nickel-cadmium batteries. • It is toxic to earthworms and causes many health problems in fish. • In humans, the main source of cadmium is exposure to cigarette smoke. – Cadmium causes lung diseases, cancer, and nervous and immune system damage. Heavy Metals (con’t) – Mercury also is found naturally. – Mercury has entered ecosystems through the burning of fossil fuels, waste incineration, mining, and the manufacture of items like batteries. • Coal burning accounts for 40 percent of the mercury released into the atmosphere. – Mercury bioaccumulates in the brain, heart and kidneys of many animals. • Mercury compounds bioaccumulate in fish, adding risk for any organisms eating fish. Persistent Pollutants! • Both DDT and PCBs are called “persistent organic pollutants” (POPs) • This is because they take a LONG time to break down HALF-LIFE = the time it takes for ½ the substance to break down Half-life (PCBs) = 8 -10 years Half-life (DDT) = 15 years Bioaccumulation • Bioaccumulation is the “build-up of chemicals in living organisms”. • The chemical accumulates because it does not break down easily (decomposers can’t break them down) • The chemicals get stored in fat-cells of organisms and can cause serious problems... NOTE: Accumulation is measured in parts per million (ppm) Bioaccumulation - EFFECTS • How it affects organisms: – Birth defects – Failure to reproduce • Amphibians live on both land and in the water. – Amphibians are sensitive to chemical changes in the environment and are valuable indicators of environmental health. – Since the 1980s, many of the world’s amphibian species have suffered declines in population. – There also have been alarming increases in amphibian birth deformities. Amphibians, like this frog, have exhibited drastic changes since the 1980s. Many theories attempt to explain these changes, including drought, increased UV rays, pollution, habitat loss, parasites, and diseases. o How BIOACCUMULATION affects ecosystems: If an important part of the food chain cannot reproduce, the whole food chain is affected. Keystone species = species that can greatly affect population numbers & health of ecosystem. Biomagnification Biomagnification is the process where chemicals accumulate AND become more concentrated at each trophic level of the food chain. ORCAS- Biomagnification • The PCB load of orcas (whales) is the highest of any animal in the world. • PCBs concentrate in the blubber of the whale • When the blubber is burned for energy, the PCBs are released into bloodstream (where they affect immune function). • Calves are born with the same PCB level as mother and then obtain more through milk. • PCB’s will affect the reproductive cycles of orcas until at least 2030. Reproductive success of BC’s resident orcas may be affected until 2030 Undoing the Damage • Science has found ways of reducing the effects of chemical pollution on the environment... BIOREMEDIATION Using living organisms (plants, bacteria) to naturally cleanup chemical pollutants through biodegradation Chemical-eating bacteria and micro-organisms can break down chemicals into non-toxic compounds! Rhodococcus bacteria can biodegrade PCBs Bacteria can be used to clean up oil spills and underground leaks A Bright Idea! Recently, scientists were able to change a gene in these chemical-eating bacteria allowing them to fluoresce (glow) when they are in contact with oil or other chemical pollutants! Bioremediation With Plants • Plants can also be used to help trap hazardous wastes such as heavy metals • The plants uptake the metals and trap them in their tissues • Plants also help stabilize by reducing wind and water erosion (that would spread contaminants).